JPS62222092A - Method and apparatus for producing praseodymium-nickel alloy - Google Patents

Abstract

PURPOSE:To efficiently produce a praseodymium-nickel alloy by electrolytically reducing praseodymium fluoride in a specified molten salt electrolytic bath with a nickel cathode and a carbon anode and by depositing the resulting praseodymium on the cathode. CONSTITUTION:Praseodymium fluoride is electrolytically reduced in a molten salt electrolytic bath with a nickel cathode and a carbon anode. The resulting praseodymium is deposited on the cathode and alloyed with the nickel forming the cathode to produce a praseodymium-nickel alloy. The molten salt electrolytic bath is composed of, by weight, 35-85% praseodymium fluoride, 10-65% lithium fluoride, <40% barium fluoride and <20% potassium fluoride.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for producing a praseodymium-nickel alloy and an apparatus for producing the same. Praseodymium with high amount and low content of impurities and inclusions -
The present invention relates to a method and apparatus for continuously producing a nickel alloy.

(Background of the Invention) Praseodymium-nickel alloy is an alloy that is expected to be used in the future as an additive for magnetic refrigeration materials and various metal materials.

By the way, the following four methods are known as methods for producing alloys of rare earth metals and high melting point metals.

First, rare earth metals are produced by molten salt electrolysis or reduction with active metals (removed as rare earth metals or alloys thereof), mixed with other metals, and dissolved.
This is a method of alloying. However, among these methods, when chloride is used as the raw material for electrolysis, handling of the raw material is difficult, and the operation is batch-type. There is a problem with that. Furthermore, when oxides of rare earth metals are electrolyzed using a fluoride electrolytic bath, the solubility of such oxide raw materials in the electrolytic bath is low, which makes continuous operation difficult, and sludge is formed at the bottom of the electrolytic bath. There is an inherent problem. In particular, in order to achieve mass production and continuous operation, it is preferable that the metal produced be in a liquid state, but in the case of high melting point rare earth metals, it is necessary to raise the electrolysis temperature to achieve this, and impurities such as furnace materials is likely to be mixed into the produced metal, making it impractical.

On the other hand, the above method, which includes the step of reducing rare earth metal raw materials using active metals, has problems in that the operation is batch-type and is not suitable for continuous large-scale production. use, requires expensive materials for reduction equipment,
Further, there are inherent problems in that the process is complicated, such as the need for a process to remove residual reducing agent components.

In the second method, a rare earth metal compound and a metal compound to be alloyed are mixed, and an appropriate compound (for example, S m -C
o In the case of alloy production, the method is to reduce with calcium hydride), but this method requires the use of an expensive reducing agent and is a punch-type operation, which is not suitable for continuous large-scale production. There are other problems.

Furthermore, thirdly, a method in which a compound of a rare earth metal and a compound of a metal to be alloyed are melted in an electrolytic bath by molten salt electrolysis, and both compounds are electrolytically reduced and deposited as an alloy on a cathode (for example, Japanese Patent No. 3298935), but this method also has the following problems. In other words, it is difficult to stabilize the composition of the alloy deposited on the cathode over a long period of time during the electrolytic process, and when oxides are used as raw materials, the solubility of the raw materials in the electrolytic bath is low, making continuous operation difficult. There are inherent problems such as difficulty in

The fourth method is the so-called consumable electrode method, in which the metal to be alloyed is used as a solid cathode, while the rare earth metal compound is dissolved in an electrolytic bath of a suitable molten salt. A method (U, S,
See Bureau of Mines, Report of Investigations, 7146 (1968), Patent No. 837401, Patent No. 967389, etc.]
It is.

However, even this method has the following drawbacks. In other words, when an oxide raw material is used as a rare earth metal compound to be electrolytically reduced, problems such as the low solubility of the oxide in the electrolytic bath and the formation of sludge may occur, as mentioned above. There is a problem, and in order to avoid this problem, high-temperature operation is required.However, when this high-temperature operation is performed, impurities from the furnace materials etc. increase, and the produced alloy becomes This will cause new problems that will reduce quality.

Moreover, in this consumable electrode method, the produced alloy is collected in a batch manner, and is not continuous, which has the inherent problem of being unsuitable for mass production.

Under these circumstances, praseodymium metal has had almost no use so far, and the reduction method in the first method mentioned above may be considered as a method for producing it in small quantities, but an industrial method for continuously producing it is not sufficient. has not been established. Therefore,
Naturally, even industrial production methods for continuously producing praseodymium-nickel master alloys have not been sufficiently established.

(Summary of the Invention) The present invention has been made in view of the above circumstances, and its object is to provide a method for continuously producing praseodymium-nickel alloy on a large scale. Another object of the present invention is to provide a reliable and economical praseodymium-nickel alloy with a high content of praseodymium and a low content of impurities and inclusions. The object of the present invention is to provide an industrial manufacturing method and apparatus.

That is, in order to achieve the above object, the present invention electrolytically reduces a praseodymium compound in a molten salt electrolytic bath using a nickel cathode and a carbon anode, and precipitates the generated praseodymium on the nickel cathode, and
When alloying with nickel constituting the cathode to form a praseodymium-nickel alloy, praseodymium fluoride is used as the praseodymium compound, and the molten salt electrolytic bath containing the praseodymium compound has a concentration of substantially 35 to 85% wt% praseodymium fluoride, 1
The praseodymium-
A nickel alloy is formed in a liquid state on the nickel cathode, and the liquid praseodymium-nickel alloy is dropped as droplets into a receiver having an opening in an electrolytic bath below the nickel cathode to form a liquid. The praseodymium-nickel alloy was collected in a layer, and the praseodymium-nickel alloy was taken out in a liquid state from the liquid layer in the receiver.

As described above, according to the present invention, a praseodymium-nickel alloy can be produced in one step of an electrolytic reduction operation, and has a low content of impurities and inclusions that adversely affect the properties of materials such as magnetic refrigeration materials. High content praseodymium-nickel alloy can be produced economically and on a large scale in one step.
This enabled continuous production.

More specifically, since a solid cathode is used, the cathode is not only easy to handle, but also the produced alloy can be taken out as a liquid alloy during electrolysis, so electrolysis can be carried out without interrupting the electrolysis. Continuous operation is possible, and as a result of continuous low-temperature operation, which is an advantage of the consumable cathode method, the electrolytic performance and the quality of the produced alloy are effectively improved.

Further, according to the present invention, it is possible to achieve large-scale and continuous operation, which is difficult to achieve with the above-mentioned reduction method using active metals such as calcium, and to suppress the contamination of impurities such as active metals. It has become possible to avoid all difficulties in continuous operation in the electrolytic production method of the fluoride-oxide mixed molten salt used as the raw material.

Furthermore, according to the present invention, it is possible to operate at a lower temperature than electrolysis using praseodymium oxide as a raw material, thereby effectively suppressing the contamination of impurities and inclusions from furnace materials etc. into the produced alloy. Furthermore, since the anode current density can be increased at the same temperature, the current can be increased when using an anode of the same size compared to the electrolytic method using the above-mentioned oxide as a raw material. , which has the advantage of improving productivity.

In addition, in the method of the present invention as described above, it is desirable that the molten salt electrolytic bath is maintained at a temperature of 800 to 1000°C, and that the electrolytic reduction operation is performed at this temperature. In, anode current density: O, OS~2.0A/cd, cathode current density:
The conditions of 0.50 to 80 A/c+4 will be suitably adopted.

Furthermore, if the molten salt electrolytic bath containing the fluoride raw material in which the electrolytic reduction operation is carried out is substantially composed of a binary system of praseodymium fluoride and lithium fluoride, at least 25% by weight of praseodymium fluoride and at least 15% by weight of the lithium fluoride
It is desirable to adjust the amount so that it is present in the electrolytic bath in the above proportion.

In carrying out the present invention, (a) a molten salt electrolytic bath consisting essentially of praseodymium fluoride and lithium fluoride, and barium fluoride and calcium fluoride added as necessary; , an electrolytic cell made of a refractory material, (b) a lining applied to the inner surface of the electrolytic cell in contact with the bath, and (C) inserted and immersed in the molten salt electrolytic bath of the electrolytic cell. (d) a longitudinal carbon anode with substantially no change in shape in the longitudinal direction; and (d) a longitudinal carbon anode with substantially no change in shape in the longitudinal direction, which is inserted and immersed in the molten salt electrolytic bath of the electrolytic cell. a nickel cathode of (e) disposed in a molten salt electrolytic bath of the electrolytic cell such that an opening is located below the nickel cathode, and an electric current is applied between the carbon anode and the nickel cathode; Droplets of praseodymium-nickel alloy produced on the nickel cathode by electrolytic reduction of praseodymium fluoride using a direct current are dropped;
an alloy receiver for collecting produced alloy droplets; (f) a liquid alloy take-out means for taking out the liquid praseodymium-nickel alloy in the alloy receiver to the outside of the electrolytic cell; and (g) a liquid alloy receiver for collecting the nickel cathode. , a cathode insertion means for inserting the praseodymium-nickel alloy into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density according to its consumption as the praseodymium-nickel alloy is produced. used.

Of course, such a praseodymium-nickel alloy manufacturing apparatus further includes an anode insertion means for inserting the carbon anode into the molten salt electrolytic bath of the electrolytic tank so as to obtain a predetermined current density, and a material as a raw material. It is desirable to have a raw material supply means for supplying praseodymium fluoride into the electrolytic cell, and the lining applied to the inner surface of the electrolytic cell may be made of a refractory metal material such as molybdenum or tungsten. Therefore, an inexpensive iron material or nickel material is preferably used.

Further, in the present invention, in order to effectively take out the liquid praseodymium-nickel alloy collected in the alloy receiver disposed in the electrolytic cell out of the electrolytic cell while keeping the liquid state, The liquid alloy extraction means is configured to have a pipe-shaped nozzle inserted into the liquid produced alloy in the alloy receiver, and through the nozzle, sucks up the produced alloy by vacuum suction and takes it out of the electrolytic cell. Doing so will be advantageously adopted from the viewpoint of industrial implementation.

(Specific explanation of the configuration) First, FIG. 1 shows a schematic diagram of an electrolytic system for carrying out the present invention. is adapted to be charged with a solvent 4 constituting a molten salt electrolytic bath.

As this solvent 4, praseodymium fluoride (P
rFz) and lithium fluoride (L i F), but in addition to these, barium fluoride (BaFz) and calcium fluoride (CaFz) can be used alone or in combination. On the other hand, the electrolytic raw material is supplied from the raw material supply device 6 into the electrolytic bath in the electrolytic cell 2, but in the present invention, the raw material is not praseodymium oxide (PraO++), but is a constituent of the electrolytic bath. Praseodymium fluoride, which is also one of the

Further, a carbon anode 8 and a nickel cathode 10 are respectively immersed in the electrolytic bath in the electrolytic bath 2, and direct current power 12 is applied between the anode 8 and the cathode 10, so that the electrolytic bath is heated. The praseodymium fluoride inside is electrolytically reduced. Through this electrolytic reduction, the cathode 10
The metal praseodymium deposited on the top immediately forms a liquid alloy with nickel constituting the cathode 10.
It drips from the surface and collects in a receiver placed in the electrolytic bath in the electrolytic cell 2. Note that at the temperature at which the above-mentioned predetermined solvent composition melts, the alloy formed on the nickel cathode 10 is in a liquid state, and the specific gravity of the electrolytic bath made of such a molten salt is equal to that of the formed alloy. As such liquid alloy is formed on the nickel cathode 10, it is smaller than the cathode 10.
It will start to fall below the surface.

Therefore, the liquid alloy collected in the receiver having the opening located below the nickel cathode 10, which receives the liquid alloy falling from the nickel cathode 10, is further transferred to the outside of the electrolytic cell 2 by the appropriate alloy extraction means 14. It will be taken out and collected.

In addition, precautions should be taken to prevent deterioration of the electrolytic bath, production stage gold, electrodes (anode 8 and cathode 10), constituent materials of the electrolytic cell, etc., and to avoid mixing harmful impurities and inclusions into the produced alloy. For this purpose, a protective gas 16 is introduced 4. In addition, the gas generated in the electrolytic cell 2 during the electrolytic reduction operation is led to the waste gas treatment device 18 together with the introduced protective gas, where it is subjected to predetermined treatment. It is now being implemented.

By the way, in the electrolytic system according to the present invention, as described above, praseodymium fluoride is used as the electrolytic raw material, unlike praseodymium oxide. When praseodymium fluoride is used as a raw material, since praseodymium fluoride itself is the main component of the electrolytic bath, it is easy to supplement the amount consumed by electrolysis by supplying it, and oxide electrolysis Electrolysis can be continued over a much wider range of raw material concentrations in the electrolytic bath than in the case of As for the method of supplying this raw material, praseodymium fluoride, it is preferable to add it to the surface of the electrolytic bath in the form of a powder, since it is instantaneous and the rate of dissolution into the electrolytic bath is fast. Introducing the powder, or by immersing a powder compact in an electrolytic bath,
It is possible to do so. Furthermore, compared to the electrolysis of praseodymium oxide, in the electrolytic operation of praseodymium fluoride, the permissible range of the concentration of the electrolytic raw material in the electrolytic region between the electrodes is much larger, and therefore the movement of the supplied raw material to this region is Even if there is a slight delay in the process, it is unlikely to interfere with the continuation of electrolysis, and therefore, regarding the supply position of the raw material praseodymium fluoride and the supply amount of electrolytic electricity, it is necessary to It has the advantage of being able to make more arbitrary selections without being subject to detailed restrictions.

In addition, in the present invention, praseodymium with less impurities
In order to produce a nickel alloy, it is necessary to lower the electrolysis temperature, and for this purpose, substantially 35 to 85% (by weight, same hereinafter) of praseodymium fluoride, 10 to 65% of praseodymium fluoride,
A mixed molten salt consisting essentially only of fluoride, consisting of up to 40% barium fluoride, and up to 20% calcium fluoride, is chosen as the electrolytic bath, and such an electrolytic Even if the above-mentioned raw material praseodymium fluoride is added to the bath, the electrolytic bath will always be adjusted to have such a composition range during electrolysis.

In addition, if the concentration of praseodymium fluoride in the electrolytic bath composition according to the present invention is less than the lower limit, that is, less than 35%, the electrolytic performance will deteriorate, and the upper limit concentration (85%)
If it exceeds this, problems such as the melting point of the electrolytic bath becoming too high will occur.

In addition, if the concentration of lithium fluoride is too low, the melting point of the electrolytic bath will rise too much, while if the concentration is too high, the reaction with the formed alloy will be intense, resulting in poor electrolysis results, etc. Since this problem occurs, its concentration needs to be adjusted to 10-65%.

Furthermore, barium fluoride and calcium fluoride are added for the purpose of reducing the amount of expensive lithium fluoride used and adjusting the melting temperature of the mixed molten salt that is formed. If there is too much, the melting point of the electrolytic bath will rise too much, so the former barium fluoride should be used in a proportion of up to 40%, and the latter calcium fluoride in a proportion of up to 20%, each alone or together. It will be used. And these four ingredients,
That is, the total amount of praseodymium fluoride, lithium fluoride, barium fluoride and calcium fluoride is substantially 100%.
In this way, an electrolytic bath is formed.

However, regarding such an electrolytic bath composition, if the electrolytic bath is a binary system consisting of only two components, praseodymium fluoride and lithium fluoride, praseodymium fluoride should account for at least 25% of the electrolytic bath. As mentioned above, it is desirable that lithium fluoride is adjusted to be present in an amount of at least 15% or more. Each fluoride used as a component of this electrolytic bath does not necessarily have to be of high purity, as long as it does not contain impurities that adversely affect the electrolytic operation or the properties of the end-use product of the produced alloy, and is usually used as an industrial raw material. Impurities that are inevitably included in the electrolytic bath may be included in the electrolytic bath without any problem as long as they are tolerable. The composition of the electrolytic solution is selected so that the electrolytic bath has a specific gravity smaller than that of the praseodymium-nickel alloy to be produced. The difference allows it to fall through the electrolytic bath and easily reach the resulting alloy receiver, which has an opening located below the cathode.

In the present invention, the temperature during electrolysis of the electrolytic bath having such a molten salt composition is preferably adjusted to a range of 800°C to 1000°C. As mentioned above, if the electrolytic bath temperature becomes too high, impurities and inclusions will be mixed into the formed alloy, and if the electrolytic bath temperature is too low, a homogeneous molten salt will not be formed. This is because it becomes difficult to form an electrolytic bath, the properties of the electrolytic bath deteriorate, and it becomes difficult to continue electrolysis. It goes without saying that it is possible to produce a praseodymium-nickel master alloy with less contamination of impurities from furnace materials etc. at the lowest possible temperature within this temperature range.

In this temperature range, a praseodymium-nickel alloy with a high praseodymium concentration containing 60% by weight or more of praseodymium can be advantageously produced, and the produced alloy is 't(9) in the receiver in this temperature range. ，
It forms N and is suitable for extraction in a liquid state. The liquid alloy in this receiver is then poured from the top of the electrolytic tank.
In addition to being able to be effectively taken out using a vacuum suction method, it is also possible to take out the material by pouring it out from below. Furthermore, when taking out the alloy, there is no need to specially heat the alloy in the receiver, and the alloy can be taken out of the electrolytic cell very easily as a liquid alloy.

Further, in the present invention, as electrodes for electrolysis, nickel is preferably used for the cathode, and carbon, particularly graphite, is preferably used for the anode. If the nickel of the cathode contains impurities, the impurities will be directly introduced into the produced alloy, so it is preferable to use a nickel material with low impurities as necessary as the nickel material of the cathode. Further, according to the present invention, as the electrolytic operation progresses, the nickel constituting the cathode produces a praseodymium-nickel alloy and is consumed, but the nickel consumed by such electrolysis is supplemented by By sequentially immersing the cathode in the electrolytic bath, the desired praseodymium-nickel alloy can be produced continuously without interrupting the electrolytic operation. In this case, it is of course possible to perform thread cutting or the like on the end of the nickel member of the cathode, and then connect the nickel members constituting the cathode one after another by threaded connection or the like to compensate for the consumed cathode portion. As described above, the fact that solid nickel can be used as a cathode is easier to handle than when molten metal is used as a cathode, and the electrolytic furnace can be simplified in terms of equipment. This is a great advantage in that it is easy to increase the size of the electrolytic furnace.

Further, in the electrolysis of praseodymium fluoride using the carbon anode according to the present invention, the current density over the entire surface of the anode is set to 0.05 to 2. It is desirable to maintain the OA/cIa within the range at all times during the electrolytic operation. However, if this current density is too low, the anode surface area will be too large or the current per unit surface area of the anode will be too small, resulting in poor productivity and no industrial advantage. In addition, if the current density becomes too high, an anode effect or similar abnormal phenomena are likely to occur when praseodymium oxide is used as a raw material. Therefore, in the present invention, it is recommended that the anode current density, which is one of the electrolytic conditions, be maintained within the above range to effectively avoid the occurrence of such abnormal phenomena. Note that, taking into account local fluctuations on the anode surface, it is more preferable to maintain the current density over the entire surface of the anode between 0.1 and 1.5 A/CIA. Furthermore, when praseodymium fluoride is used as a raw material, the anode current density can be higher at the same temperature than when praseodymium oxide is used as a raw material, which is preferable from the point of view of actual operation.

On the other hand, the current density of the cathode is allowed over a wide range of 0.50 to 80 A/cut over the entire surface of the cathode. However, if the cathode current density is too low, the current per unit surface area of the cathode will be too small, resulting in poor productivity and not being industrially viable. In addition, if this cathode current density is too high (too much), the electrolysis voltage will increase significantly and the electrolysis results will deteriorate.In addition, when continuing the actual electrolysis operation, it is necessary to use a narrower cathode current density of 1.0 to 30 A/cffl. Maintaining the current density within the range keeps the electrolysis voltage fluctuation range narrow and facilitates electrolysis operation.
It can be said that it is more preferable.

Furthermore, according to the present invention, carbon, which is different from the bath-resistant material of the electrolytic bath, is used as the anode, unlike the case where the bath-resistant container (bath-resistant material) of the electrolytic bath also serves as the anode. ,
There is no need to terminate the electrolysis due to consumption of the anode; it is only necessary to compensate for the consumption and further immerse the anode in the electrolytic bath, or, since a plurality of anodes are used, to replace them with new anodes one by one. Similarly, the cathode only needs to be immersed in an electrolytic bath to compensate for its consumption, or replaced with a new cathode. In the present invention, due to the large difference in the surface current density ratio between the anode and cathode, it is preferable to use an electrode arrangement in which a plurality of anodes are arranged around each cathode so that the anode faces the cathode. In such cases, if the anodes are replaced sequentially, praseodymium-nickel alloy can be produced continuously without interrupting the electrolytic operation. , the advantages of the electrolytic method can be fully utilized. Moreover, since both the anode shape and the cathode shape can be used with an external shape that does not substantially change in the length direction, there will be no inconvenience caused in their continuous use. be.

A preferred example of the structure of an electrolytic cell implementing the present invention is schematically shown in FIG.

In FIG. 2, the electrolytic cell 20 is composed of a lower tank 22 and a lid 24 that covers the opening thereof. The outer sides of the lower tank 22 and the lid body 24 are usually constructed of tank outer frames 26 and 28 made of metal such as steel.

Further, the lower tank 22 and the lid body 24 are each coated with a fireproof insulation material I made of brick, castable alumina, etc.
T! ! 30. 32, and bath-resistant material layers 34 and 36 made of graphite, carbonaceous stamp material, etc. are arranged inside.

A lining material 38 is provided on the inner bath-contact surface of the inner bath-resistant material layer 34 of the lower tank 22 to cover the bath-contact surface. This lining material 38 is a bath-resistant material layer 34.
In addition to preventing the contamination of impurities from tungsten or molybdenum, if it is made of a refractory metal such as tungsten or molybdenum, it can also serve as a receiver for the liquid praseodymium-nickel alloy that is produced. However, in the present invention, it is recommended to use an iron material or a nickel material, which is cheaper than refractory metals, as the lining material 38. Further, the bath-resistant material layer 34 is not necessarily required, and there is no problem in applying the lining material 38 directly on the fire-resistant heat insulating material layer 30.

Further, one or more nickel cathodes 40 and a plurality of carbon anodes 42 arranged opposite to the nickel cathodes 40 are provided so as to penetrate through the lid body 24.
Further, both electrodes 40 and 42 are immersed in an electrolytic bath 44 made of the predetermined molten salt housed in the lower tank 22 over a length that provides a predetermined current density. Note that here, two of the carbon anodes 42, 42 are shown among the anodes disposed facing the nickel cathode 40, and graphite is preferably used as their material.

Further, these carbon anodes 42, 42 are used in the form of rods, plates, tubes, etc., and in order to increase the anode surface area of the part immersed in the electrolytic bath 44 and lower the anode current density, grooves are formed as known in the art. It can also be attached. In addition, in FIG. 2, the carbon anode 42 has a slight slope at the anode immersion part, showing traces of anode wear due to electrolysis. There is no problem even if an electric lead made of a suitable conductor such as metal is attached to the anode 42 for power supply. Also,
The anode 42 can be moved up and down by an anode lifting mechanism 46 serving as an anode insertion means, and can be moved intermittently or continuously to ensure an appropriate anode current density for continuous electrolysis. Specifically, the surface area of the immersion part can be adjusted by adjusting the immersion depth. Note that the anode lifting/lowering mechanism 46° 46 can also have the function of electrically connecting to the anode.

On the other hand, the cathode 40 is made of nickel to be alloyed with metal praseodymium deposited by electrolytic reduction, one of which is shown here. Also,
In FIG. 2, the cathode immersion area is shown in a conical shape, showing traces of cathode consumption due to droplet formation of the praseodymium-nickel alloy.

Since the electrolysis temperature is selected to be below the melting point of nickel of the cathode 40, the nickel cathode 40 is solid and is used in the form of a wire, rod, plate, tube, or the like. The nickel cathode 40 is also continuously or intermittently fed into the electrolytic bath 44 by a cathode lifting mechanism 48 serving as a cathode insertion means to compensate for the bone lost due to alloy formation. The cathode lifting mechanism 48 can also have the function of electrically connecting to the cathode. Furthermore, there is no problem if the surface of the nickel cathode 40 other than the immersed part is protected with a suitable protective sleeve or the like for corrosion prevention.

Further, in the electrolytic bath 44, a produced alloy receiver 50 is arranged on the bottom of the lower tank 22 so that the receiver opening is located below the nickel cathode 40, and the nickel cathode is The liquid praseodymium-nickel alloy 52 produced on the cathode 40 drips from the surface of the cathode and is collected in the produced alloy receiver 5o which opens just below. The produced alloy receiver 50 is formed using a refractory metal that has low reactivity with the produced alloy 52, such as tungsten, tantalum, molybdenum, niobium, or an alloy thereof, or a boron such as boron nitride. Ceramics such as compounds and oxides, or materials such as cermets,
Furthermore, it can also be formed using nickel.

The electrolytic bath 44 is made of a fluoride mixed molten salt containing praseodymium fluoride, whose composition is adjusted according to the present invention as described above, and whose specific gravity is the same as that of the praseodymium-nickel alloy to be produced. Selected so that the specific gravity is below. The electrolytic raw material consumed by electrolysis is supplied from a raw material supply device 54 through a raw material supply hole 56 provided in the lid 24, so that the electrolytic bath 44 of a predetermined composition is maintained.

In addition, when a predetermined amount of generated alloy 52 drips from the nickel cathode 40 and accumulates in the receiver 50, it is removed from the electrolytic cell 20 in a liquid state by a predetermined alloy recovery mechanism (retrieval means). However, in the present invention, as shown in FIG.
0 into the electrolytic bath 44, the tip of the nozzle 58 is immersed in the produced alloy 52 in the produced alloy receiver 50, and the produced alloy is sucked using the vacuum suction action of a vacuum device (not shown). 52 to electrolytic tank 2
Means for extracting the value outside of 0 will be advantageously employed.

However, instead of using such a vacuum suction method to take out the produced alloy 52, an extraction pipe is provided that penetrates the lower part of the electrolytic cell 20 (lower tank 22), and the tip of this extraction pipe is further connected to the produced alloy receiver 50. It is also possible to adopt an alloy recovery mechanism in which the formed alloy 52 is flowed out of the furnace and downward through the take-out pipe by penetrating the pipe and opening into the receiver 50.

Although not shown, a protective gas is supplied into the electrolytic furnace 20, and the gas generated by the electrolytic operation is discharged to the outside through the waste gas outlet 62 together with the protective gas. It is designed to be ejected. Further, although such an electrolytic cell 20 is not provided with a special heating device for maintaining the electrolysis temperature described above, in order to maintain the electrolysis temperature at a predetermined temperature, the inside of this electrolytic cell 20 may be heated as necessary. It goes without saying that a suitable heating device may be provided inside or outside the heating device.

(Examples) In order to clarify the present invention more specifically, Examples according to the present invention will be shown below, but the present invention should not be construed in any way in a limited manner by the description of such Examples. It goes without saying that.

In addition to the detailed explanation of the present invention and the following examples, the present invention can be implemented in various B types, and as long as it does not depart from the spirit of the present invention,
It should be understood that any of the various embodiments that can be implemented based on the knowledge of those skilled in the art belong to the scope of the present invention.

Example 1 Rare earth metal-nickel (RE-Ni) alloy 1.61 k having an average composition of rare earth metal mainly consisting of praseodymium = 67% (on a weight basis; the same applies hereinafter) and nickel: 33%
g was obtained as follows.

That is, in an apparatus having a configuration similar to the electrolytic cell shown in Fig. 2, a graphite crucible lined with nickel is used as the bath-resistant material of the electrolytic cell, and a molybdenum crucible is installed at the center of the bottom of the graphite crucible as a receptacle for the produced alloy. Using a container, an electrolytic bath consisting of a binary fluoride mixed molten salt consisting essentially of praseodymium fluoride and lithium fluoride was electrolyzed in an inert gas atmosphere at an average electrolysis temperature of 830°C. As a cathode, a piece of
A +nφ nickel wire was used, and four 40 mmφ graphite rods were used as anodes, arranged concentrically around the cathode (in planar form) and immersed in the electrolytic bath.

Using praseodymium fluoride as a raw material, electrolysis was carried out for 16 hours while continuously supplying the powder to the electrolytic bath and maintaining the electrolytic conditions within the range shown in Table 1 below.

During this period, electrolysis operations were able to continue extremely well.
A liquid rare earth metal (praseodymium)-nickel alloy was dripped in sequence and collected in a molybdenum receiver placed in an electrolytic bath. This accumulated alloy is released every 8 hours.
The alloy was taken out of the electrolytic furnace using a vacuum suction type alloy recovery device equipped with a vacuum suction nozzle.

The electrolytic results obtained by such electrolytic operation and the analysis results of the produced alloy are shown in Tables 1 and 2 below. Note that the current efficiency was determined based on the weight of the recovered rare earth metal (all assumed to be praseodymium).

Table 1 Table 2 As is clear from the results in Tables 1 and 2, by electrolyzing praseodymium fluoride according to the present invention, a praseodymium-nickel alloy with a high praseodymium content can be produced all at once. It has been observed that such produced alloys are praseodymium-nickel alloys with a low content of impurities that deteriorate the alloy properties. Note that the numerical values of the alloy-containing components in Table 2 are the average values of the analysis values of the alloy taken out every 8 hours.

Further, in the above examples, it is easy to continue electrolysis for a longer period of time, and it has been confirmed that similar results can be obtained even in such a case.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a specific electrolytic system for implementing the present invention, and FIG. 2 is a sectional view showing an example of the structure of an electrolytic cell for implementing the present invention. 2: Electrolytic cell 4: Solvent 6: Raw material supply device 8: Carbon anode 10: Nickel cathode 12: Electric power 14: Alloy extraction means 16: Protective gas 18: Waste gas treatment device 20: Electrolytic cell 22: Lower tank 24: M body 30.32 = Fireproof insulation material layer 34.36: Bath-resistant material layer 38 Lining material 40: Nisokel cathode 42: Carbon anode 44: Electrolytic bath 46: Anode lifting mechanism 48: Cathode lifting mechanism 50: Generated alloy receiver 52: Produced alloy 54: Raw material supply device 58: Vacuum suction nozzle 60: Produced alloy suction hole Applicant: Sumitomo Light Metal Industries, Ltd. Figure 1

Claims (11)

[Claims] (1) Using a nickel cathode and a carbon anode, a praseodymium compound is electrolytically reduced in a molten salt electrolytic bath, and the generated praseodymium is deposited on the nickel cathode and alloyed with the nickel constituting the cathode,
In forming the praseodymium-nickel alloy, praseodymium fluoride is used as the praseodymium compound, and the molten salt electrolytic bath containing the praseodymium compound contains substantially 35 to 85% by weight of praseodymium fluoride and 10 to 65% by weight of praseodymium fluoride. of lithium fluoride, up to 40% by weight barium fluoride and up to 20% by weight calcium fluoride, while forming the praseodymium-nickel alloy in a liquid state on the nickel cathode; Then, the praseodymium-nickel alloy in the liquid state is dropped as droplets into a receiver having an opening in the electrolytic bath below the nickel cathode to collect as a liquid layer, and further, from the liquid layer in the receiver, A method for producing a praseodymium-nickel alloy, characterized in that the praseodymium-nickel alloy is extracted in a liquid state. (2) The manufacturing method according to claim 1, wherein the molten salt electrolytic bath is maintained at a temperature of 800 to 1000°C, and the electrolytic reduction operation is performed at this temperature. (3) The electrolytic reduction operation has an anode current density of 0.05 to
2.0A/cm^2, cathode current density: 0.50-80A
The manufacturing method according to claim 1 or 2, which is carried out under conditions of /cm^2. (4) The manufacturing method according to any one of claims 1 to 3, wherein the carbon anode is a graphite electrode. (5) The molten salt electrolytic bath containing the praseodymium compound is
Claims essentially consisting of praseodymium fluoride and lithium fluoride, and adjusted so that the praseodymium fluoride is present at least 25% by weight or more, and the lithium fluoride is present at least 15% by weight, respectively. The manufacturing method according to any one of items 1 to 4. (6) An electrolytic cell constructed of a refractory material and containing a molten salt electrolytic bath consisting essentially of praseodymium fluoride and lithium fluoride, as well as barium fluoride and calcium fluoride added as necessary. , a lining provided on the inner surface of the electrolytic cell in contact with the bath; a longitudinal carbon anode that is inserted into and immersed in the molten salt electrolytic bath of the electrolytic cell and whose shape does not substantially change in the longitudinal direction; , an elongated nickel cathode whose shape does not substantially change in the longitudinal direction, which is inserted and immersed in the molten salt electrolytic bath of the electrolytic tank, and an opening located below the nickel cathode; A liquid of praseodymium-nickel alloy formed on the nickel cathode by electrolytic reduction of praseodymium fluoride by direct current applied between the carbon anode and the nickel cathode, which is placed in the molten salt electrolytic bath of the electrolytic cell. an alloy receiver for collecting the praseodymium-nickel alloy droplets into which the droplets are dropped; a liquid alloy take-out means for taking out the liquid praseodymium-nickel alloy in the alloy receiver to the outside of the electrolytic cell; and cathode insertion means for inserting a nickel cathode into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density according to its consumption as the praseodymium-nickel alloy is produced. A praseodymium-nickel alloy production device characterized by: (7) The manufacturing apparatus according to claim 6, further comprising anode insertion means for inserting the carbon anode into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density. (8) The manufacturing apparatus according to claim 6 or 7, further comprising a raw material supply means for supplying praseodymium fluoride as a raw material into the electrolytic cell. (9) The liquid alloy extraction means has a pipe-shaped nozzle inserted into the liquid praseodymium-nickel alloy in the alloy receiver, and sucks up the praseodymium-nickel alloy through the nozzle by vacuum suction, and The manufacturing apparatus according to any one of claims 6 to 8, which is adapted to be taken out. (10) The manufacturing apparatus according to any one of claims 6 to 9, wherein the lining is made of an iron material or a nickel material. (11) The manufacturing apparatus according to any one of claims 6 to 10, wherein the carbon electrode is a graphite electrode.